This invention relates to the field of agglomeration of mineral ores and more particularly to agglomeration of directly reduced metallized particles. An extremely large number of binder compositions have been developed and patented over the years. However, no binder is known to be suitable for agglomerating highly metallized finely divided particulates such as iron fines from direct reduction process, a steel mill, a foundry or the like without oxidizing the metallic fines. More particularly, a significant percentage of finely divided iron particulates or fines are produced in the operation of a direct reduction furnace whereby iron ore or pellets are reduced to highly metallized particles such as pellets or lumps, by direct contact with a reducing gas such as a mixture of hydrogen and carbon monoxide. These fines are normally discarded or stockpiled and constitute a waste material inasmuch as there has been no suitable binder available for agglomerating these fines. Sintering or other treating method normally causes oxidation of the fines which thereupon required an additional reduction step. This is, of course, extremely inefficient inasmuch as the particulates are reduced twice.
Another method for utilizing fines that has been tried is to seal the fines into drums and charge the drums filled with fines into a steelmaking furnace. This is an extremely expensive method of recovering the fines because of high handling costs and drum expense. In addition, the finely divided particles constitute a health hazard for workers as well as a dust problem in the furnace.
Briquets have been found to be a very desirable charge material in iron or steelmaking. They are particularly suitable for foundries. The high specific gravity enables briquets to penetrate the slag layer on a molten metal bath in an induction furnace more readily than other, lighter charge materials. The large size of briquets prevents them from trickling through a furnace charge as is common with fine materials, particularly when employed as a charge material for cupolas. Briquets made in accordance with the teachings of the present invention have higher carbon levels than normal charge materials. This reduces the necessity for recarburization of the metal produced. The quality of the present binder allows the addition of coke breeze, ferro-alloys and other materials to the briquets, which can be stored and handled in the same manner as steel scrap. The high strength of the briquets, their water-proof bond, and the rust inhibiting properties of the binder allow outdoor storage and generally rough handling. The binder composition also makes it possible to tailor-make briquets for particular applications.